High-speed rotary tool holder



Oct. 15, 1963 M. GARNIER ETAL 3,107,101

HIGH-SPEED ROTARY TOOL HOLDER Filed March 7, 1961 2 Sheets-Sheet 1 Oct.15, 1963 Filed March 7, 1961 M. GARNIEYR EI'AL HIGH-SPEED ROTARY TOOLHOLDER 2 Sheets-Sheet 2 United States Patent 3,107,101 HIGH-SPEED ROTARYTUOL HOLDER Marcel Garnier and Henri Lonard, Besancon (Boobs),

France, assignors, by mesue assignments, to Soeietc Anonyme Micro-Mega,Besancon, France, a company of France Filed Mar. 7, 1961, Ser. No.93,928 5 Claims. 21. 279-41) This invention relates to mounting meansfor highspeed rotating tools, especially hand tools, and still morespecifically tools as used in dental surgery in connection with dentalengines of the kind having high-speed rotating means, e.g. an air-spunturbine, for rotating the tool.

The application to dental tool holders constitutes a preferred aspect ofthis invention and the objects and advantages of the invention Willaccordingly be described with primary reference to such specific use.

With the increasingly high velocities of tool rotation that arecurrently being used in the dental art it is becoming more and moredifficult to provide a satisfactory mounting device for the tool in thenon-revolving support provided on the extension arm of a dental engine.Such mounting device, besides permitting quick and easy insertion andremoval of the tool for readily changing from one type of tool toanother, must be of such character as to retain the tool very firmlywhen inserted, since at the extremely high angu ar velocitiesinvolvedsometimes as high as 300,000 revolutions per minuteany clearanceor backlash in the mounting assembly however slight will rapidly beamplified by centrifugal force to produce vibrations of substantialamplitude constituting a hazard both to the patient and the equipment.

For a similar reason it is required that the revolving assemblycomprising the tool and its holder should be journalled in the supportwith great accuracy since any out-of-center condition will be amplifiedby centrifugal force with similar objectionable results.

At the high angular drive speeds here referred to, the load torquerequired to be developed when working with the tool is comparativelyvery low, corresponding to a Working pressure of about 20 grams, and theturbine is arranged to stall if the pressure exceeds say about 50 grams.

It has already been proposed to provide a tool holder in the form of anelastic sleeve or tube of non-metallic material in which the tool shankis resiliently gripped and which is journalled in bearings of thesupport. However the non-metallic materials from which such elastic toolholders have been made tend to Wear, harden and/ or deform with time,whereupon the stringent conditions mentioned above are no longerfulfilled by them.

In another type of resilient tool holder of the prior art, the toolshank and holder have been provided with coacting tapers and theresilient tool gripping action provided by spring means forcing the toolshank into the tapered recess of the holder. This type of mountingdevice has been found unsatisfactory chiefly because it lacked rigidityand at the high speeds contemplated the spring was incapable ofrestraining the tool in position against the powerful action of thecentrifugal forces generated.

In another known type of resilient tool holder, the holder has beenprovided as a longtiudinally slotted sleeve. While this construction hasavoided many of the drawbacks mentioned above, such a slotted tubularconstruction has not been generally capable of providing the smooth,continuous bearing surfaces required for journalling the holder in thebearing surfaces of the support, and imperfect dynamic balancing waspresent. The slot or slots had to be formed with extremely smalltransverse dimensions so that they were rapidly clogged with dirt andthe requisite radial resiliency of the holder was no longer present.

It is generally an object of this invention to provide an improvedmounting means for =a1high-speed rotating tool, which will besubstantially free of the various drawbacks listed above. Specificobjects of the invention are to provide an all-metallic tool holder thatwill have substantial radial resiliency for firmly gripping the tool toensure vibration-free support thereof even at the highest rotationalvelocities that may be encountered in practice; and to provide such aresilient holder that will nevertheless have smooth, continuouscylindrical bearing surfaces for perfect rotational support incorresponding nonrevolving bearings. Another important object is toprovide such a holder that can be conveniently machined from an integralpiece of steel tubing so that extremely close machining tolerances canbe maintained. Further specific objects are to provide various forms ofsuch tubular holders combined with integral rotating means therefor: inone form of the invention such rotating means may comprise a rotor foran air-turbine secured to or formed integrally with one end of theholder, and in another form the rotating means may comprise a gearannulus secured to or formed integrally around the holder. Other objectsinclude the provision of improved methods of manufacturing the toolholder of the invention.

The tool holder embodying the invention may, in one form, comprise anintegral metallic body of tubular cylindrical shape having a pair ofdiametrically opposed longitudinal slots formed over an intermediatelongitudinal portion of said body, arcuate segmental apertures being cutin the body adjacent the opposite ends of the slots and each apertureextending circumferentially from one wall of one slot to a point shortof a wall of the other slot. The slots and apertures thus define a pairof opposed segmental flanges and oppositely-extending longitudinal armsintegrally projecting from opposite ends of the respective flanges,which arms are integrally interconnected at their outer ends by endportions of the body beyond the opposite ends of the slots. These endportions provide cylindrical outer bearing surfaces adapt ed to bejournalled in correspondin ly spaced inner hearing surfaces of thenon-rotatable support. The tool is adapted to be inserted through theaxial aperture in one of said end portions into engagement with theinner surfaces of the segmental flanges, to be forcibly yet resilientlyretained thereby for rotation with the holder.

Exemplary embodiments of the invention will now be described for purposeof illustration but not of limitation with reference to the accompanyingdrawings, wherein:

FIG. 1 is a side elevational view or" an improved tool holder accordingto the invention;

FIG. 2 is a cross section on line IIII of FIG. 1;

FIG. 3 is a sectional view similar to FIG. 2, but illustrates a toolshank inserted into the holder;

FIG. 4 is a perspective view of an embodiment of the inventioncomprising a tool holder generally similar to that of FIGS. 1-3, butfurther including a drive gear thereon; and

PEG. 5 is a sectional View of a tool holder according to FIG. 4 mountedwithin a support provided on an arm of a dental engine, of the type inwhich the axis of tool rotation is at right angles to the longitudinaldimension of the arm.

The improved tool holder illustrated is desirably made from a singleintegral length of stainless steel tubin and the peculiar form of theholder of the invention can best be explained by describing the variousmachining steps to which this length of tubing is subjected.

Machined or other-wise formed) in an intermediate section of the tubularbody, are a pair of diametrically 3 opposed, longitudinal slots 9 andiii, which extend short of the respective ends of said body, so as toleave full cylindrical end portions designated 5 and 6. Desirably, onewall of each slot 9 and 19 may be bevelled as shown in FIG. 2.

Next, two pairs of cuts are made through the wall of the tubular body,adjacent the respective ends of the slots. Thus there is a first pair ofcuts 11 and 12 adjacent the end portion 5 and another pair of cuts 13and 14 adjacent the end portion 6 of the body. Each cut in each pairextends from one wall of one of the slots, in a circumferentialdirection around the tubular body, as far as a point short of the nearwall of the other slot. The resulting anr-angement is perhaps mostclearly seen in FIG. 4, and it will be apparent that there have thusbeen provided a pair of segmental, arcuate or part-cylindrical flangesland 2, which extend in reverse circumferential directions around thetube and are positioned in generally diametrically opposed relationshiptherearound. Moreover, because of the manner in which the cuts 11-12,and i32l4 are made, there is a pair of aligned arms, 3 and 4respectively, extending from the opposite longitudinal ends of theflanges. These arms are integrally interconnected at their outer endswith one another by way of the longitudinal end portions 5 and 6 of thetubular body. In the embodiment of FIGS. 13, these end portions areuncut and may have substantially the same outer and inner diameters asthe initial length of tubing.

It will be evident that there has thus been provided an all-metallic,one-piece tool holder which includes an intermediate section that isslotted to be capable of resiliently gripping the shank of a toolinserted into the holder through the aperture 8 in one of the endportions, say end portion 6, as will be later described, and which alsoincludes two end portions that are not slotted but are provided withcontinuous cylindrical surfaces capable of acting as rigid, accuratebearing surfaces in cooperation with correspondingly axially-spacedinner bearing surfaces of a non-rotatable support in which the holder isto be journalled.

After the body has been machined in the manner described, the twosegmental flanges 1 and 2 are preferably each distorted or bent inwardlyby a small amount, and the part is then exposed to an annealing,quenching and tempering treatment, or any other suitable heat treatment,

for imparting the desired resiliency and hardness characteristics to themetal in its deformed condition. The distorted condition of the flanges1 and 2 is apparent from the showing of FIG. 2, and it will beunderstood that the dimensioning is such that the tool shank can beforcibly yet readily inserted into the tubular body to force the flanges1 and 2 outwards to their initial undefor-rned shape, as shown in F G.3, thereby providing a firm grip of the holder about the tool.

The embodiment just described with reference to FIGS. 1 to 3 isespecially suitable for use in connection with a dental engine toolsupport of the type in which the tool holder and tool are driven inrotation by a direct drive from one end of the holder. Thus, the endportion 5 of the holder of FIG. 1 may be adapted for force-fitengagement with the rotor of an air turbine positioned in the support.According to a desirable modification (not shown) of this form of theinvention the air-spun rotor of the turbine may be formed integrallywith the tubular body of the holder, whereby the rigidity andconcentricity of the revolving assembly are even further enhanced.

'FIG. 4 illustrates a somewhat modified embodiment which is'especiallysuitable for use with a dental engine tool support in which the axis oftool rotation is at right angles to the axis of rotation of the turbineor other rotating means used. In this case, a gear 15 is secured aroundthe tubular body. near one of its end portions, beyond the correspondingends of the slots. According to a preferred modification of thisembodiment, the gear 15 may be formed integrally with the body. Theembodiment of FIG. 4 further differs from the first-described embodimentin that the end portions 5 and d have a somewhat smaller outer diameterthan the initial tube diameter, and an abutting flange 5a is providedbetween the end portion 5 and the main body portion.- Further the outerend of body portion 5 is sealed with an integral web or end wall 5b. Thereasons for these minor modifications will appear presently.

HG. 5 illustrates the tool holder of FIG. 4 mounted in a support of therectangular-drive type above referred to. it will be noted that theholder is inserted in a recess of the support with the outer surfaceofend portion 5 seated in an upper bearing sleeve 38 of the support, andthe upper side of flange 5a abutted against a corresponding shoulder ofthe support. A threaded cover insert or plug 17 containing anotherbearing sleeve 19 is then passed around the lower end portion 6 of theholder and is screwed into a corresponding screw threaded opening ofrecess until the upper end face of sleeve 19 abuts against the lower endface of gear 15. In this position gear 15 meshes with a gearannulusprovided at one end of a shaft 15 journalled in the support at rightangles to the tool axis and driven from a suitable power means (notshown).

A lubricating aperture 2% is provi ed at the upper end of tne supportand it will be noted that owing to the sealing web 5b at the top of theholder the lubricant will serve to lubricate the coo erating bearingsurfaces. While smooth bearings have been shown and implied so far, itwill be appreciated that any desired type of antifriction bearings maybe provided instead if desired for mounting the holder in the support.

Whatever the particular form of embodiment used, a

tool holder constructed in accordance with the inventionshows superiorperformance, at high and very high speeds of tool rotation, to any ofthe holder constructions heretofore proposed. This is due in part. tothe fact that the holder, while being of one-piece construction andhence strong and easily machina-ble to close tolerances, is yet of acomposite character, in that it simultaneously presents a resilientintermediate portion for gripping the tool shank and rigid continuousend portions for providing perfect bearing support. The resilientsegmental flanges 1 and Z are integrally connected with the end portionsthrough the arm portions 3 and which work as torsion bars, by twistingabout their centers of gravity G (FIGS. 2 and 3) when the flanges 1 and2 are forced outwards on insertion of the tool shank. The slots 9 andit": can be made quite wide and chamfered as shown, and are not liableto be clogged up with dirt so that the resilient grip on the tool shankis not impaired.

When the rigid revolving assembly comprising the tool and its holder isjournalled in its support, there is positively no radial clearanceexcept between the cooperating bearing surfaces of the holder and thesupport, and this can be reduced to a very low and accuratelycontrollable value by current machining techniques.

Even at the highest drive speeds that may be encountered and highattendant values of centrifugfl force, the holder of the inventionprovides smooth vibrationless rotation for indefinitely long periods oftime.

It will be understood that various changes may be introduced into theembodiments illustrated and described without exceeding the scope of theinvention claimed.

What we claim is:

1. A tool holder for a high-speed rotary tool comprising a generallytubular body including a resilient intermediate portion for gripping theshank of a tool inserted into said body and non-resilient continuousgenerally cylindrical end portions for rotatable engagement in hearingsurfaces of a support, said intermediate portion comprising segmentalgenerally part-cylindrical flanges and longitudinal ann portionsconnecting said flanges with the respective end portions for resilienttorsional deformation of said flanges about said arms on gripping a toolshank, at least one of said end portions being perforate for insertionof said tool shank therethrough into gripping engagement with anintermediate portion.

2. A tool holder for a high-speed rotary tool comprising a generallytubular one-piece body including a resilient intermediate portion forgripping the shank of a tool inserted into said body and non-resilient,continuous generally cylindrical end portions for rotatable engagementin bearing surfaces of a support, said intermediate portion comprising apair of segmental flanges cut out of the tubular Wall of said body anddiametrically-opposed longitudinal arm portions integrally connectingsaid flanges with the respective end portions for resilient torsionaldeformation of said flanges about said arms on gripping a tool shank, atleast one of said end portions being perforate for insertion of a toolshank therethrough into gripping engagement with said intermediateportion.

3. A tool holder for rotatable insertion in a non-revolving supporthaving axially spaced bearing surfaces and into driven engagement with ahigh-speed rotating means, comprising an integral metallic body ofgenerally tubular cylindric form, said body having a pair ofdiametrically opposed longitudinal slots formed over an intermediatelongitudinal portion of said tubular body, said body further havingarcuate segmental apertures being formed in said body adjacent theopposite ends of said slots and each extending circumferentially from arelated one of said slots to a point short of the other slot, so thatsaid slots and apertures cooperate to define a pair of opposed segmentalflanges and oppositely-extending longitudinal arms integrally projectingfrom opposite ends of the re spective flanges, said arms beingintegrally interconnected at their outer ends by end portions of saidbody beyond the opposite ends of said slots, at least one of said endportions having an axial opening for insertion of a tool therethroughinto forcible yet resilient engagement with the inner surfaces of saidsegmental flanges for rotation With said holder.

4. The tool holder claimed in claim 3, wherein said flanges aredistorted in a radially inward direction for increasing the forcibleresilient engagement of a tool therewith.

5. The combination with a tool holder as claimed in claim 3 of a gearrigid with and coaXially surounding said body to constitute meansthrough which the tool holder is adapted to be rotatably driven from ahigh speed rotating means.

References Cited in the file of this patent UNITED STATES PATENTS1,597,404 Crossley Aug. 24, 1926 1,646,771 Shefler Oct. 25, 19272,087,868 Baxendale July 20, 1937 2,341,744 Shefler Feb. 15, 19442,842,839 Benjamin July 15, 1958 2,989,317 Staunt June 20, 1961

1. A TOOL HOLDER FOR A HIGH-SPEED ROTARY TOOL COMPRISING A GENERALLYTUBULAR BODY INCLUDING A RESILIENT INTERMEDIATE PORTION FOR GRIPPING THESHANK OF A TOOL INSERTED INTO SAID BODY AND NON-RESILIENT CONTINUOUSGENERALLY CYLINDRICAL END PORTIONS FOR ROTATABLE ENGAGEMENT IN BEARINGSURFACES OF A SUPPORT, SAID INTERMEDIATE PORTION COMPRISING SEGMENTALGENERALLY PART-CYLINDRICAL FLANGES AND LONGITUDINAL ARM PORTIONSCONNECTING SAID FLANGES WITH THE RESPECTIVE END PORTIONS FOR RESILIENTTORSIONAL DEFOR